With the development of integrated circuit towards ultra-large scale integrated circuit, circuit density in the integrated circuit continues increasing, the number of components included in the integrated circuit continues increasing, and the size of the components decreases accordingly. With the decreasing of the size of metal-oxide-semiconductor (MOS) devices, channels of the MOS devices are shortened accordingly. Because the channel is shortened, the gradient channel approximation of the MOS devices is no longer valid, and varieties of adverse physical effects (especially the short-channel effect) become prominent. The device performance and reliability may degrade, which limits further reduction of the size of the devices.
To further reduce the size of the MOS devices, a multifaceted-gate field effect transistor (FET) structure has been developed to improve the control capability of the gate on the MOS device, and to suppress the short-channel effect. Among them, a fin field effect transistor (FinFET) is one of common multifaceted-gate field effect transistors.
The FinFET has a three-dimensional structure. The FinFET includes a substrate, one or more protruding fins formed on the substrate, and an isolation structure disposed between adjacent fins. The FinFET also includes a gate electrode crossing the one or more fins and covering each of top and sidewall surfaces of the fins. Because the three-dimensional FinFET is significantly different from a conventional planar transistor, improper operations in some processes may cause a great impact on the electrical properties of the formed device.
A source region, a drain region, and a channel of the FinFET are formed in the fin, and, thus, the formation quality of the fin has an important influence on the performance of the semiconductor structure. However, the fins in the FinFET often have non-uniform height or width, thereby affecting the performance of the formed semiconductor structure. The disclosed methods and device structures are directed to solve one or more problems set forth above and other problems.